1. Technical Field
The following description relates to an image formation device and an image formation method.
2. Related Art
An image formation device for forming an image on a print medium (e.g. paper) uses high-voltage electric power for various electrophotographic processes (steps) such as charging, exposure, development, image transfer and fixation. Among the processes, the charging process involves a problem in that the charging function of a charging unit for electrically charging a photosensitive body (e.g. photosensitive drum) is easily deteriorated by contamination (stains, oxidation) of a charging wire of the charging unit. In a conventional technology for resolving the problem, the charging function of the charging unit is maintained by successively increasing a target value (for constant-potential control (constant electric potential control) of the charging wire) stepwise in response to the decrease in the charging voltage of the photosensitive body. When the target value exceeds an electric potential that can cause an electric leak or failure to the charging unit, the user is requested to clean the charging wire.
However, the conventional technology (just restricting the target value) is incapable of preventing spark discharge (full-path dielectric breakdown) which is caused by a temporary increase (transient rise) in the electric potential of the charging wire. Since the spark discharge damages the charging unit and the photosensitive body and seriously deteriorates the image quality, the request to the user for the cleaning of the charging unit has to be made frequently for the prevention of the spark discharge.